Typical of the prior art synthesis of cyclic oxide copolymers is U.S. Pat. No. 3,344,088 which describes the copolymerization of tetrahydrofuran and propylene oxide or ethylene oxide utilizing SiF.sub.4 as a catalyst. The patent discusses very low concentrations of the ethylene oxide or propylene oxide, e.g., five parts or less by weight based upon 100 parts of the tetrahydrofuran which, as might be expected, yields a solid crystalline product.
Similarly, copolymerization of tetrahydrofuran and ethylene oxide is also the subject of U.S. Pat. Nos. 3,359,332 and 3,644,567, each utilizing different catalysts. However, the amount of ethylene oxide utilized in the former patent is relatively low, that is one part in ten or 20 of tetrahydrofuran and generally a molar amount equal to the molar amount of the catalyst is employed. As such, the ethylene oxide merely functions as a co-catalyst in the polymerization of the tetrahydrofuran and hence, a crystalline product is obtained. The latter patent provides for the preparation of block copolymers of tetrahydrofuran and ethylene oxide as well as other monomers, but utilizing approximately equal amounts of both monomers.
None of these patents discusses the usefulness of a relatively low amount of ethylene oxide and a corresponding high percentage of primary hydroxyl end groups in a propylene oxide-containing copolymer, much less a method for preparing such a product. Thus, while these desirable properties have been sought, we have not seen a specific polymeric composition having these characteristics heretofore.